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<h1 style="text-align: center;">Cluster Data</h1>
<h2 style="text-align: center;">(overview)</h2>
<div style="text-align: center;"><img alt="Data Classes (UML)"
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            <td colspan="2" rowspan="1" style="vertical-align: top;">DataDescriptor</td>
            <td style="vertical-align: top;">Describes the data.<br>
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            <td style="vertical-align: top;">dataID<br>
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            <td style="vertical-align: top;">String<br>
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            <td style="vertical-align: top;">An identifier for the data.<br>
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            <td style="vertical-align: top;">nodes<br>
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            <td style="vertical-align: top;">Collection&lt;String&gt;<br>
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            <td style="vertical-align: top;">Names of nodes that own or
access the data.<br>
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            <td style="vertical-align: top;">pf<br>
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            <td style="vertical-align: top;">PartitionFunction<br>
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            <td style="vertical-align: top;">Function for partitioning
the data.<br>
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            <td style="vertical-align: top;">skf<br>
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            <td style="vertical-align: top;">StringKeyFunction<br>
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            <td style="vertical-align: top;">Function for transforming
a string into a key that can be partitioned.<br>
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Format,Distribution, ...<br>
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Data can be partitioned on input or output.<br>
When the stored data is unpartitioned, an input descriptor uses a
partition function to separate the work between the nodes.<br>
When the stored data has already been partitioned on output using an
output data descriptor with a partition function, the data need not be
partitioned on input.<br>
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